Power Master problem

[SPOOLN]

Hello members,

I am having a problem with my power master. The electric pump keeps on running and will not pull the fluid into the accumulator. I had a leaking rear wheel cylinder and replaced it and then bleed the entire system. The pump motor still continues to run. The system worked fine before i had parked the car for 3 years. Any help would be appreciated
Thanks

 

[gofstbuick]

Rebuild the master cylinder. Probably the check valve or power piston is allowing fluid to seep past the power assist system

 

[SPOOLN]

I have a rebuild kit , i will give it a try.
Thanks

 

[SPOOLN]

Power master

Great News i fixed my problem. It was the electric booster motor. Yes on the hydrualic side. I took the end piece apart and found that the pump tumblers were sticking from brake vanish in fact 3 of them. Reassembled everything very carefully and rebleed the system. Brakes again!!!! I hope this helps other members with a similar problem.. All these GNs that have low miles and sitting need to be cycled to prevent parts for varnishing up.

 

[gofstbuick]

Glad you fixed your system. Very interesting. Can you elaborate further. When I rebuilt my PM master cylinder, there was black goo every where. I tried to clean it as best I could. I know there is still some left in the motor. If I too could take my motor apart, that would give me more peace of mind. Please email me some additonal details, or shoot me a phone number (via email) we'll talk.

 

[SPOOLN]

Hey Gofst,
On the electric pump motor, there are two sides. One is the hydraulic side and the other is electric. There is a snap ring that holds the end cap in place. You have to gently press the end cap so the snap ring can unlock. You will need a awl or pick to lift the o ring. the cap will come off. Be sure to clean around the snap ring first because of dirt and such. There is a seal underneath the cap. Be careful not to damage the seal. Once the seal is removed you will see the plate that covers the tumblers. Those tumblers are designed to move in and out. That was where mine were vanished and sticking. I have driven my car for 500 miles now and everthing works great. Remember the two reservors are seperate looking down the center form front. The right side is only for your wheel brakes and the left is for the electric booster/acuumulator,switch. Your master cylinder internal seals is what seperates the two. It is a very simple principal and easy to work on. Understanding how this system works i would not even consider changing over to vacuum.

 

[gofstbuick]

thank you, I didn't know I could take the motor apart. I understand the hydraulics of the master cylinder and PM reservoir. I rebuilt my MC a while back and there was black gunk all over. I also built a test adapter to allow me to see the PM hydraulic pressure. The adapter goes between the pressure switch and master cylinder. You hook a brake gauge to the third leg of the tee and then you can see if the pressure readings are in range. I suspect that there is varnish build up in the motor and will attempt to take it apart this weekend. The instructions for build ig the adapter is in a thread in the brake forum. The actual GM tool is $1500. A little too much for the average home technician. The tool I built, including the purchase of brake gauges is around $130-150 depending on your machinist skills.